JPH02308131A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the deterioration in characteristics and to improve a display grade by forming another light shielding film on the semiconductor switching elements on one substrate thereby obviating the incidence of light onto the semiconductor switching elements. CONSTITUTION:The semiconductor switching elements 10 and picture element electrodes 7 are formed on one substrate 19 of a pair of the substrates 18, 19. Counter electrodes 14 are formed in accordance with the picture element electrodes 7 on the other substrate 18. The light shielding films 12 are disposed in correspondence to the semiconductor switching elements. The incidence of the light to the semiconductor switching elements is prevented by the light shielding films 12 on the other substrate 18 and since another light shielding film 11 is formed on the semiconductor switching elements 10 of the one substrate 19, the light by, for example, multiple reflections, to the semiconductor switching elements 10 is surely prevented. The deterioration in the characteristics of the semiconductor switching elements by light is prevented in this way and the display grade is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a liquid crystal display device such as an active matrix type liquid crystal display device to which a thin film transistor is added, and more specifically, the present invention relates to a liquid crystal display device such as an active matrix type liquid crystal display device to which thin film transistors are added. The present invention relates to a liquid crystal display device suitably used as a transmission type liquid crystal display device for projection.

Prior Art FIG. 3 is a simplified plan view of a typical prior art;
FIG. 4 is a sectional view taken along section line IV-4 in FIG. 3. With reference to these drawings, in an active matrix liquid crystal display device for a projection device,
On one glass substrate 35, a source bus electrode 20,
The gate bus electrodes 21 are insulated from each other via an insulating film 27, and are formed in a matrix in the form of a lattice. A thin film transistor (abbreviated as TPT), which is a semiconductor switching element, is formed on the glass substrate 35 , and its channel portion 23 is connected to the source electrode 2 in relation to the gate bus electrode 21 .
2 and the drain electrode 24, and the source electrode 2
2 is connected to the source bus electrode 20 and the drain electrode 24
is connected to a picture element electrode 26 formed of a transparent conductive film. A wiring film 33 is formed on the thin film transistor 28 and the picture element type [i26]. Another glass substrate 3
4, a thin film transistor 28, a source bus electrode 20
A light shielding film 25 is formed corresponding to the gate bus electrode 21 . A transparent conductive film 31 is formed over the entire surface of the region where the light shielding film 25 is formed and the remaining region of the glass substrate 34, and an orientation J132 is formed thereon.

The light-shielding film 25 is shown by hatching in FIG. 3, and is in a light-transmitting state when no voltage is applied between the picture element electrode 26 and the electrode 31, and is in a non-transparent state when a voltage is applied.
Display can be performed in a so-called normally white mode.

The light shielding film 25 covers the picture element electrode 26 and the source bus electrode 2.
0 and the gate bus electrode 21 to improve display contrast and color reproducibility. This light shielding M25 is made of metal or colored synthetic resin. When using a colored synthetic resin, its visible light transmittance is 4.5 μm thick DARC (trade name: Bre
1% (500
nm), 2% (700 nm), 1.1 u with 1.5 μm color mosaic CK (product name: manufactured by Fuji Hunt Co., Ltd.)
3% with JDS (product name: manufactured by Nippon Synthetic Rubber Co., Ltd.)
(450 nm).

When such a liquid crystal display device is used in, for example, a projection device, a strong light amount ranging from several times to several tens of times that of sunlight is irradiated from above in FIG. When strong light is incident in this way, when the light shielding film 25 is made of colored synthetic resin, the light leaking through the light shielding film 25 reaches the thin film transistor 28, and this light shielding film 2
When 5 is made of metal or colored synthetic resin, there is a problem that light due to multiple reflections of light incident on the liquid crystal display device reaches the thin film transistor 28, and the threshold voltage of the thin film transistor 28 shifts due to long-term operation. . This causes a significant deterioration in display quality.

Problems to be Solved by the Invention An object of the present invention is to provide a liquid crystal display device that does not cause deterioration in display quality due to light.

Means for Solving the Problems The present invention applies a potential to a picture element electrode via a semiconductor switching element formed on one substrate, and applies a potential to a picture element electrode corresponding to the picture element electrode on the other transparent substrate. In the liquid crystal display device, a liquid crystal is filled between the two substrates, and a light-shielding film is arranged on the other substrate in correspondence with the semiconductor switching element. Another one on the semiconductor switching element
This is a liquid crystal display device characterized in that two light shielding films are formed.

According to the present invention, a light shielding film is formed on the other substrate corresponding to the semiconductor switching element, thereby preventing light from directly entering the semiconductor switching element.

Further, on the one substrate, another light shielding film is formed on the semiconductor switching element.

Therefore, the light leaking through the light shielding film on the other substrate is blocked by the light shielding film on this semiconductor switching element,
In addition, the light that entered the liquid crystal display device and was reflected multiple times,
The light is shielded by the light shielding film on the semiconductor switching element. Therefore, no light is incident on the semiconductor switching element. This prevents deterioration of characteristics,
Display quality can be improved.

Another light shielding film may be formed on the semiconductor switching element on the one substrate as described above, and this light shielding film may also be formed on the one substrate in a region other than the picture element electrode. This not only prevents light from leaking between the picture element electrode formed on the one substrate and conductors such as the source bus electrode and gate bus electrode, but also prevents light from leaking from the opening of the light shielding film. By increasing the area as much as possible, it is possible to prevent the aperture ratio from decreasing. In the prior art shown in FIGS. 3 and 4 described above, the light shielding film 25
is formed on the substrate 34 corresponding to the remaining area other than the picture element electrode 26, and such a light shielding film 25 is formed on the substrate 34.
In order to prevent light leakage from between the picture element electrode 26 and the source bus electrode 20 and gate bus electrode 21 even if the relative positions of A so-called margin is required by making mtIi of the unformed opening smaller than the picture element electrode 26. Therefore, in the prior art of FIGS. 3 and 4,
There is a problem that the area of the opening region where the light shielding film 25 is not formed is relatively small and the aperture ratio is reduced. By forming another light-shielding film over conductors such as bus electrodes and gate bus electrodes, there is no need for a margin for misalignment of the pair of substrates, thereby preventing a reduction in the aperture ratio. , it is now possible to perform a bright display.

Display quality can be improved.

Embodiment FIG. 1 is a simplified plan view of an embodiment of the present invention.
FIG. 2 is a sectional view taken along the section line ``--'''' in FIG. 1.

A plurality of gate bus electrodes 2 are formed on one glass substrate 19 at intervals. This gate bus electrode 2
is made of metals such as tantalum, titanium, molybdenum, and aluminum.

An insulating film 8 made of tantalum oxide or silicon nitride is formed on this gate bus electrode 2. A semiconductor film made of amorphous silicon or the like is formed on this substrate 19, and further an amorphous silicon film is formed on this substrate 19. The thin film transistor 10, which is a semiconductor switching element, is thus formed. In the channel portion 4 of the thin film transistor 1o, the source bus electrode 1 is formed of the same metal as the zero-order gate bus electrode 2 between the source electrode 3 and the drain electrode 5.

In this way, the source bus electrode 1 and the gate bus electrode 2 are formed in a matrix shape by depositing indium tin oxide by zero-order sputtering or the like, applying photoresist, exposing it to a predetermined pattern, developing it, and then hydrogen bromide. A pixel electrode 7 connected to the train electrode 5 is formed by etching with acid.

Next, a light shielding film 11 is formed. This light-shielding fill is made of a colored synthetic resin material, and its thickness needs to be at least about 1 μm in order to obtain sufficient light-shielding properties. Shading [
The material for the colored synthetic resin No. 11 is Color Mosaic CK (black synthetic resin with carbon black dispersed in it).
(product name: manufactured by Fuji Hunt Co., Ltd.) or Color Mosaic CB (product name: manufactured by Fuji Hunt Co., Ltd.), which is a dark synthetic resin in which blue pigment is dispersed. In this case, spin cord, offset After applying the film to a predetermined thickness by printing, spraying, dipping, or other methods, it was heated at 85°C for 2 minutes, and after applying oxygen-blocking WRM made of polyvinyl alcohol, it was heated again at 85°C for 2 minutes to form a film of 40 mg. /cm'' in a prescribed pattern, heated again at 85°C for 2 minutes, developed with a prescribed developer for 1 minute, and washed with pure water.
The light shielding film 11 is obtained by heating at 200'C for 5 minutes.

When JDS (product name: manufactured by Japan Synthetic Rubber Co., Ltd.), which is a resin dyed with black dye, is used as the colored synthetic resin material for light-shielding 7111, it can be printed using methods such as spin cording, offset printing, spraying, and dipping. After coating to a predetermined film thickness, it was heated at 140°C for 30 minutes, exposed to a predetermined pattern with ultraviolet light of about 30 mg/cm2, developed with pure water for 1 minute, and then
Heat at 'C for 30JI+. So Black-18
1 (manufactured by Nippon Kayaku) in an aqueous solution of 1% acetic acid and 2% acetic acid at 60°C.
After dyeing by dipping for 0 minutes, wash with pure water and incubate at 180'C.
The film is dried for 10 minutes to obtain a light-shielding film 11.

On this light-shielding Jllll, an alignment layer 11 made of polyimide is placed.
115 is formed, and orientation treatment is performed by a rubbing method.

The light shielding film 11 formed in this manner is shown in FIG. 1 by diagonal lines slanting from the upper right to the lower left.

On the other glass substrate 18, in order to form the light shielding film 12, tantalum is first vapor-deposited and a photoresist 0FPR is applied.
-800 (trade name: manufactured by Tokyo Ohka) is applied to a predetermined thickness using a spin cord, heated at 85° C. for 30 minutes, then exposed to a predetermined pattern, developed, and washed with pure water. After further heating at 130°C for 30 minutes, dry etching was carried out in CF, followed by immersion in acetone and 0.05°C. By performing ashing treatment using plasma, the remaining resist is removed and a light shielding layer 1112 is obtained. A transparent electrode 14 made of indium tin oxide or the like is formed thereon, and an alignment layer 1116 made of polyimide is further formed, and an alignment treatment is performed by a rubbing method.

These two substrates 18 and 19 are bonded together, and nematic liquid crystal 17 is encapsulated therein. Here, as a liquid crystal display device for a projection device, a panel of about 5 inches or less is considered to be a reasonable size from the viewpoint of compatibility with an optical system or manufacturing cost. The light shielding film 12 is indicated by diagonal lines slanting from the upper left to the lower right in FIG. 1, and is disposed directly above the thin film transistor 10. The light-shielding film 12 is made of tantalum, metal, and has excellent light-shielding properties as described above. Therefore, when strong light is incident from above in FIG. 2, it is possible to prevent the light from leaking into the thin film transistor 10.

As mentioned above, the light-shielding film 11 is made of colored synthetic resin, and by dispersing dye or pigment in the light-transmitting synthetic resin, the transmittance in the visible light range of 400 to 700 nm can be increased to 10.
% or less. Examples of this synthetic resin material include:
It may be polyimide, polyamide, polyurea, polyurethane, acrylic, polyquinamic acid, cyclized rubber, naphthoquinone azide and derivatives thereof.

The light shield 11111 covers the thin film transistor 10, the source bus electrode 1, and the gate bus electrode 2, and is open at the pixel electrode 7. This prevents light from entering the thin film transistor 10 as described above, and also protects the glass substrate 1.
Even if a mutual positional shift of 8.19 occurs, the margin described in connection with the prior art described above is not necessary, and a reduction in the aperture ratio can be prevented, and the pixel electrode 7 and the bus electrode 1
．． It is possible to prevent light leakage from between the two and the display contrast and color reproducibility can be improved.

According to the experimental results of the inventor of the present invention, when the light transmittance of the light shielding film 11 is 15%, the display contrast is '40, and when the light transmittance is 10%, the display contrast is sufficient for a normal television receiver. It was confirmed that a display contrast of 50, which is the minimum required for obtaining image quality, could be obtained. When the light transmittance was set to 15%, a shift in the threshold voltage of the thin film transistor 10 was observed due to light leakage from the light shielding film 11, but when the light transmittance was set to 10%, such a phenomenon did not occur. confirmed.

By setting the light transmittance to 10% or less, higher definition and smaller size can be achieved.

In addition to the above-mentioned tantalum, the light-shielding film 12 may be made of a metal material such as chromium, or may be made of the colored synthetic resin material mentioned above as the material of the light-shielding film 12.

As still another embodiment of the present invention, a thin film transistor l
An electrically insulating protective layer is formed on O, and a light shielding film 11 is formed on it.
Alternatively, a layer made of a metal material may be formed.

The present invention can be implemented not only in connection with a transmissive liquid crystal display device, but also by using the substrate 19 as a light-shielding film, for example.
It can also be implemented in connection with a so-called reflective liquid crystal display device. Instead of the thin film transistor 10, a semiconductor switching element having another configuration may be used.

Effects of the Invention As described above, according to the present invention, a semiconductor switching element and a picture element electrode are formed on one of a pair of substrates, and a semiconductor switching element and a picture element electrode are formed on the other substrate, facing each other in correspondence with the picture element electrode. The electrode is formed, and a light shielding film is arranged corresponding to the semiconductor switching element, and the light shielding film on the other substrate prevents light from entering the semiconductor switching element, and the semiconductor switching element on the one substrate is prevented from entering the semiconductor switching element. Since another light shielding film is formed also on the switching element, it is possible to reliably prevent light, for example, due to multiple reflections, from entering the semiconductor switching element. Therefore, deterioration of the characteristics of the semiconductor switching element due to light can be prevented and display quality can be improved.

[Brief Description of the Drawings] Fig. 1 is a simplified plan view of one embodiment of the present invention, Fig. 2 is a sectional view taken along the section line ■-■ in Fig. 1, and Fig. 3 is a prior art FIG. 4 is a cross-sectional view taken along the section line rV-4 in FIG. 3.

Claims (1)

[Claims] One potential is applied to a picture element electrode through a semiconductor switching element formed on one substrate, and a counter electrode is formed on the other transparent substrate corresponding to the picture element electrode. In a liquid crystal display device, a liquid crystal is filled between the two substrates, and a light shielding film is disposed on the other substrate in correspondence with the semiconductor switching element. , one more
A liquid crystal display device characterized in that two light shielding films are formed.